Persistence of glyphosate, and associated influence on available nutrients, in native plant tissues following sublethal herbicide application in northern British Columbia forests
Bibliographic record
Abstract
Glyphosate-based herbicides (GBH) are highly effective, nonselective herbicides that have been used in British Columbia’s forest industry since the early 1980s to remove deciduous vegetation competing with commercially important coniferous tree seedlings. Long term persistence of glyphosate and its metabolic byproduct aminomethylphosphonic acid (AMPA) in the forest ecosystem has not previously been monitored beyond one year, although it is known that glyphosate may be stored in tissues of plants that received a sublethal dose of GBH. The primary objective of this research thesis was to determine the duration (up to twelve years) of glyphosate and AMPA persistence in the roots, shoots, and fruits of selected perennial plant species in GBH-treated forest cutblocks. Due to the ability of glyphosate to form insoluble complexes with metal ions, it was suspected that metal nutrient concentrations in surviving plants might be affected by persistent glyphosate. The second main objective of this thesis was to determine if concentrations of calcium (Ca), iron (Fe), magnesium (Mg), manganese (Mn), nickel (Ni) and zinc (Zn) were significantly altered by GBH treatment. Plant tissue samples from five forest understory perennial species growing in two distinct biogeoclimatic (BEC) zones of northern BC were analyzed for glyphosate and AMPA content, and comparisons were made between species, plant tissue type, and BEC zone. Residues persisted for up to 12 years in some tissue types, and root tissues generally retained glyphosate residues longer than shoot tissue types. Samples from the drier, colder, more northern Boreal White and Black Spruce (BWBS) BEC zone retained significantly higher levels of glyphosate for longer than samples collected from the warmer Sub-Boreal Spruce (SBS) BEC zone. Shoot samples from three species in the SBS zone were further analyzed for nutrient contents. Nutrient concentrations were more variable over time in treated samples than in control samples, and comparison of treated and control samples resulted in significant differences in 47 % of all cases, and in 61 % of year one samples. Generally, Ca, Mg and Ni decreased with treatment in all three species; Zn increased with treatment for each species; and Fe and Mn had inconsistent changes with treatment. Both the persistence of glyphosate and related changes in plant nutrient concentrations may have cumulative health effects for wildlife. More research should be conducted in this field, as many questions remain unanswered.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".